1. Field of the Invention
The present invention relates to a full color digital image reproducing apparatus such as a full color copying machine which can also reproduce a monochromatic image in addition to a full color image.
2. Description of the Prior Art
A full color digital image reproducing apparatus, such as a full color copying machine, has a monochromatic color copy mode in addition to a full color copy mode. In the monochromatic color copy mode, gradation data are obtained from color data of red, green and blue, and a monochromatic image is reconstructed from the gradation data for color data of cyan or the like.
However, the monochromatic color mode has problems. Spectral luminous efficiency of human eyes corresponds to a mixing ratio of about 3:6:1 for three primary colors of red, green and blue. Then, yellow having a low mixing ratio becomes whitish yellow, and red becomes thin. Then, a reproduced image seems to be strange as compared to an actual image. Further, the reproduced image is insufficient even for reproducing monochromatic information and for communicating information in the image.
Then, it may be proposed to provide gradation data for flat or average frequency characteristic by using a mixing ratio of 1:1:1 for three primary colors of red, green and blue. However, in this case, differences in colors may not be reproduced as differences in gradations when various color information exists in a document. For example, even an image in a back face of a document may be reproduced, or a colored background may be reproduced for example when a document has a colored background.
Further, usually, a user selects a reproduction color by designating a name of the color. However, the name of the color does not necessarily agree with a color desired really by a user. Further, a color reproduced by a machine may not be necessarily kept the same when there is a change in an environment thereof.